#!/bin/sh

# Copyright (c) 2012 The Chromium OS Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

# Backchannel control script - sets up and tears down backchannel network
# interfaces. Backchannel interfaces are hidden from flimflam and will never be
# the default route.
#
# A backchannel interface can also be used to simulate a cellular
# modem used by fake-cromo if the new interface name is set to
# pseudo-modem0
#

test_if=eth_test

usage () {
	echo "Usage: $0 <command> [args...]"
	echo "  setup <iface> [new_iface_name]    Sets <iface> as the backchannel device"
	echo "  teardown <iface> [new_iface_name] Returns the backchannel device to normal"
	echo "  reach <ip> <gw> [new_iface_name]  Inserts routes to <ip> via gateway <gw>"
}

macaddr () {
	ip addr show "$1" | awk '/link\/ether/ { print $2 }'
}

ipaddr_with_subnet_mask () {
	ip addr show "$1" | awk '/inet / { print $2 }'
}

# We need to down the interface (and therefore stop flimflam) across the
# invocation of nameif, according to nameif(1).
renameif () {
	old="$1" ; shift
	new="$1" ; shift
	initctl stop shill
	ip link set "$old" down
	nameif "$new" $(macaddr "$old")
	ip link set "$new" up
	initctl start shill
}

setup () {
	oldip=$(ipaddr_with_subnet_mask "$1")
	if [ ! -z $2 ] ; then
		test_if="$2"
	fi
	renameif "$1" "$test_if"
        ip addr add "$oldip" dev "$test_if"
}

teardown () {
        if [ ! -z $2 ] ; then
		test_if="$2"
	fi
	renameif "$test_if" "$1"
}

reach () {
	ip="$1" ; shift
	gw="$1" ; shift
        if [ ! -z $1 ] ; then
		test_if="$1"
	fi
	ip route add "$ip" via "$gw" dev "$test_if"
}

if [ -z "$1" ]; then
	usage
	exit 1
fi

command="$1" ; shift
case "$command" in
	setup)
		setup "$@"
		;;
	teardown)
		teardown "$@"
		;;
	reach)
		reach "$@"
		;;
	*)
		usage
		;;
esac
